From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish. NASA engineers are still giddy after a successful landing on Mars.

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UNIDENTIFIED MAN #1: It's the wheel. It's the wheel.

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UNIDENTIFIED MAN #2: We can see a wheel image.

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UNIDENTIFIED MAN #2: We are wheels down on Mars.

CORNISH: At 10:32 p.m. Pacific Time last night, a one-ton, six-wheeled rover named Curiosity landed gently in a crater on Mars. Moments later, to their surprise and delight, engineers got the first pictures back from their new Mars outpost. Earlier today, NASA released color pictures taken by the rover as it descended to the surface. NPR science correspondent Joe Palca sent this story from NASA's Jet Propulsion Laboratory in Pasadena, California.

JOE PALCA, BYLINE: There are a lot of very tired, very happy people here at JPL. Anxiety kept people awake before the landing, and jubilation had the same effect afterwards. People were particularly ecstatic about some small, grainy, black-and-white images that arrived shortly after landing. At a news conference this morning, Curiosity mission systems manager Michael Watkins gave a more realistic assessment of what the rover has provided up until now.

MICHAEL WATKINS: Now that we're all, you know, awake and we've digested this and we have a little bit less adrenaline that it's not such a great picture anymore, right? Right?

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WATKINS: It's beautiful to us, right? It's beautiful to us because of what it means, but you can see there's a lot of stuff on the lens there, and that is actually dust kicked up by the landing event.

PALCA: And through the dust, you can make out some rocks in the foreground, what could be the rim of a crater off in the distance and a lovely shot of the rover's left rear wheel. But Watkins says these first black-and-white images are special.

WATKINS: I really love these images because, you know, later we're going to get magnificent color panoramas and 3-D images and magnificent things on Mars, but these first images somehow are always the best ones to me, because when you land on Mars, it's new every time.

PALCA: Project scientist John Grotzinger said there was something about seeing pictures that made the landing seemed more real.

JOHN GROTZINGER: And when you see that wheel on the ground, you know you've landed on Mars. No semaphore tones, no people jumping up and down, you actually see a picture of the surface of the planet with a spacecraft on it, and that is the miracle of engineering.

PALCA: There was one truly spectacular image for the landing, but it wasn't taken by the rover. It came from a camera known as HiRISE on the Mars Reconnaissance Orbiter orbiting more than 200 miles above the planet. Sarah Milkovich is a JPL scientist working with HiRISE.

SARAH MILKOVICH: We normally take pictures of the surface, but this time we actually took a picture with HiRISE as MSL came in on the parachute.

PALCA: MSL is an acronym scientists use for the rover.

MILKOVICH: So you can see the little dot there is MSL moving across. The box shows our image. There's the parachute.

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PALCA: You can actually see the capsule that's surrounding the rover dangling from a giant parachute above the surface of Mars. It's an incredible, unforgettable image, a picture of a spacecraft landing on another planet taken from another spacecraft. Data and images will continue to trickle down from the rover over the coming hours and days. The first images will be taken mainly to make sure all the cameras are working properly, not so much for scientific investigations.

Engineers want to move slowly with the rover. It's a complicated machine, and it has the power to operate for years, even decades, so they don't want to screw it up on the opening days. Everything went so well last night that in hindsight it's almost hard to image there was anything to worry about. Miguel San Martin is chief engineer for guidance and control of the rover mission. He says engineers were confident before landing.

MIGUEL SAN MARTIN: If we didn't feel that it was doable or we felt there's no chance of success, we would not be doing it. That said, I mean, we trained ourselves for eight years to think the worse all the time. You know, you're in the shower thinking what thing can give you a bad day. I mean, that's what you do. I mean, it's constantly thinking ways that things can go wrong, so you can go and do something about it, and then you can never turn that off.